1. Field of the Invention
The present invention relates to an air-purifying filter for decomposing NOx, CO, sulfur compounds, cigarette odor and other hazardous components in the air, entering or generated in a passenger compartment of an automobile, for example. The present invention also relates to an air-purifier utilizing the air-purifying filter which is compact in size and suitable to be mounted in an automobile.
2. Description of the Prior Art
Various kinds of air-purifiers for an automobile have been proposed and practiced for purifying air containing dusts and contaminants. The prior art air-purifier includes a cartridge having an active carbon that adsorbs dust and contaminants in the air while the air passes therethrough under pressure.
In many of the prior art air-purifiers, a disposable type adsorbent such as an active carbon have been used in the cartridge. The adsorbent needs to be replaced at relatively short intervals, which is uneconomical. When the adsorbent is used for a longer period of time without timely exchange, it becomes incapable of purifying the air.
Another type air-purifier has been known in Japanese patent publication (JPA) No. 1-234729, which eliminates odor generated and existing in a compartment of an automobile, for example. This air purifier or deodorizer has an adsorbent supporting a photocatalyst that will decompose odor components adsorbed by the adsorbent when being subjected to irradiation. This deodorizer has a long-lived deodorization capability.
Gases entering or generated in an automobile passenger compartment include many kinds of poisonous, harmful or hazardous components such as NOx, CO, sulfur compounds and cigarette odor. Photocatalysts such as those proposed in the above-mentioned JPA No. 1-234729 have been proved to be effective to eliminate odor components and NOx. In the meantime, platinum group catalysts such as Pd have been known to effectively oxidize and eliminate CO. Thus, in order to eliminate NOx, CO and odor components in the air, in accordance with the prior art technology, it would be necessary to employ a composite air-purifier having a first filter supporting a photocatalyst mainly for oxidized decomposition of NOx and another filter supporting a platinum group catalyst effective in main to eliminate CO by its oxidized decomposition. Such a composite air-purifier would be large and difficult to mount in an automobile.
On the other hand, sulfur compounds such as SOx and H.sub.2 S poison the platinum group catalysts. When the platinum group catalyst is continuously used for a long period of time in an atmosphere containing poisonous components including NOx, CO and sulfur compounds, it is gradually poisoned by the sulfur compounds and loses its catalyst activity. Therefore, the prior art air-purifying filter is not practically useful to be mounted in an automobile where the entering or existing gas contains mixed poisonous components including NOx, CO, sulfur compounds and cigarette odor.